Contractors active in Maryland county permit records, grouped from public filings. Counts reflect permits attributed to each firm. Not every filing names a contractor, so counts here are a floor. A firm's actual permit activity is usually higher.
| Contractor | Trade | Counties | Permits | Last active |
|---|---|---|---|---|
| CONSTELLATION HOME | HVAC | Frederick County, Howard County | 363 | Jul 2026 |
| SUNRUN INSTALLATION SERVICES INC | Solar | Frederick County, Howard County | 267 | Jul 2026 |
| ENVIRONMENTAL SYSTEMS ASSOCIATES LLC DBA CROPPMETCALFE | HVAC | Howard County | 154 | Jul 2026 |
| AT YOUR SERVICE REPAIR, INC. | Plumbing | Frederick County, Howard County | 116 | Jul 2026 |
| SOLAR ENERGY WORLD | Solar | Frederick County, Howard County | 109 | Jul 2026 |
| FUSION SOLAR SERVICES LLC | Solar | Frederick County, Howard County | 106 | Jul 2026 |
| CECO, INC | Electrical | Frederick County, Howard County | 84 | Jul 2026 |
| HEIL PLUMBING | Plumbing | Howard County | 77 | Jul 2026 |
| BRYANT GROUP, INC. | Plumbing | Frederick County | 75 | Jul 2026 |
| JENSON FIRE PROTECTION INC | Fire Protection | Frederick County | 73 | Jul 2026 |
| TESLA ENERGY OPERATIONS INC | Solar | Howard County | 64 | Jul 2026 |
| ANTHONYS ELECTRIC | HVAC | Howard County | 61 | Jul 2026 |
| ERIC SMOCK HEATING & A/C INC | HVAC | Frederick County | 56 | Jul 2026 |
| MEGA PLUMBING CORP | Plumbing | Frederick County, Howard County | 54 | Jul 2026 |
| KENNETH J LEMERE/SPARTAN ELEC | Electrical | Frederick County | 50 | Jul 2026 |
| AMERICAN RESIDENTIAL SERVICES, ARS OF LAUREL #8551 | HVAC | Howard County | 47 | Jul 2026 |
| Fence & Deck Connection | Deck & Patio | Baltimore County, Frederick County, Howard County | 47 | Jul 2026 |
| Andrew Weinberg | Deck & Patio | Baltimore County | 45 | Jun 2026 |
| CELESTIAL SOLAR INNOVATIONS LLC | Solar | Frederick County, Howard County | 44 | Jul 2026 |
| EHRHARDT QUALITY PLUMBING | Plumbing | Howard County | 42 | Jul 2026 |
| ADT Security LLC | Electrical | Frederick County | 38 | Jul 2026 |
| ALBAUGH AND SONS FENCING | Deck & Patio | Frederick County | 34 | Jul 2026 |
| CULLIGAN WATER TREATMENT | Plumbing | Frederick County | 34 | Jul 2026 |
| HORIZON SERVICES MD LLC | HVAC | Howard County | 34 | Jul 2026 |
| D & L CLEAN POWER SOLUTIONS LLC | Solar | Frederick County, Howard County | 33 | Jun 2026 |
| BLAZEGUARD, INC. | Fire Protection | Frederick County | 32 | Jul 2026 |
| Ramiro A Fernandez | Electrical | Frederick County | 28 | Jul 2026 |
| ROBERT A TULL INC | Plumbing | Frederick County | 28 | Jul 2026 |
| BRYAN DOUGLAS LAW | Solar | Howard County | 27 | Jun 2026 |
| LEN THE PLUMBER | Plumbing | Howard County | 27 | Jul 2026 |
| CHEASAPEAKE PLUMBING & HEATING | Plumbing | Frederick County | 26 | Jun 2026 |
| PROVIDENT ELECTRIC | Electrical | Frederick County, Howard County | 26 | Jul 2026 |
| TRI STAR ELECTRIC INC | Accessory Structure | Howard County | 24 | Jul 2026 |
| MICHAEL AND SON SERVICES, INC. | HVAC | Frederick County, Howard County | 23 | Jul 2026 |
| Tesla Energy Operations, Inc. Tesla Energy Operations, Inc. | Solar | Frederick County | 23 | Jul 2026 |
| TRINITY SOLAR LLC | Solar | Frederick County, Howard County | 23 | Jun 2026 |
| UNITED AIR TEMP | HVAC | Frederick County, Howard County | 23 | Jul 2026 |
| D. W. BAHR PLUMBING | Plumbing | Howard County | 22 | Jul 2026 |
| BEN LEWIS INC | Plumbing | Frederick County | 21 | Jul 2026 |
| HORIZON SERVICES | HVAC | Howard County | 21 | Jul 2026 |
| TRI-STATE HOME SERVICES | HVAC | Frederick County | 21 | Jul 2026 |
| CLARKSVILLE CONSTRUCTION SERVICES | Deck & Patio | Howard County | 20 | Jul 2026 |
| SILVER DOLLAR ELECTRIC INC. | Accessory Structure | Frederick County, Howard County | 20 | Jul 2026 |
| J. A. SMITH & CO. INC. | Plumbing | Frederick County, Howard County | 19 | Jul 2026 |
| NORTHERN CROSS ELECTRIC INC | Electrical | Howard County | 19 | Jul 2026 |
| PUTMAN PLUMBING INC | HVAC | Frederick County | 19 | Jul 2026 |
| BLUE DOT SERVICES | HVAC | Howard County | 18 | Jul 2026 |
| BRYAN MOBERLY PLUMBING SERVICES | HVAC | Howard County | 18 | Jul 2026 |
| David Williams Electric | Accessory Structure | Howard County | 18 | Jul 2026 |
| ERCOLE ELECTRIC INC | Electrical | Frederick County | 18 | Jul 2026 |
Source: county permit records. Updated monthly.